Heart: An international team of researchers led by Ian Reid of the University of Auckland reviewed 11 separate clinical trials involving 12000 patients and found that calcium supplements were associated with about a 30% increase in heart attack risk. The chances of stroke and mortality also increased to a lesser extent. The link was consistent across trials and was independent of age sex and type of supplement.
Bones: John Cleland and colleagues of the University of Hull: Calcium supplements are probably not efficient in reducing bone fractures.